Known automatic or automated motor vehicle transmissions generally comprise a parking lock, with which an output shaft of the transmission can be mechanically fixed. In addition to a purely mechanical system for actuating such a parking lock by way of a mechanical operative interaction between a selector lever that can be operated by the driver, the lever being provided on the inside of the motor vehicle, and the parking mechanism in the transmission, electromechanical and electrohydraulic systems are also known for actuating such a parking mechanism, for example from DE 4127991 C2, wherein the parking lock in the transmission is connected via an electric operative connection to a selector device inside of the motor vehicle that can be operated by the driver, and wherein the parking lock can be electromechanically or electrohydraulically actuated by way of a parking lock function implemented in an electronic controller of the transmission, as a function of a position chosen on the selector device and as a function of other operating parameters of the motor vehicle.
Furthermore, various methods for automatically engaging such a parking mechanism are known. For example, U.S. Pat. No. 3,937,105 proposes automatically engaging the parking lock of the transmission, independently of the position selected by the driver, if an ignition circuit of the motor vehicle is interrupted and at the same time the motor vehicle still coasts at a speed below a defined low threshold value.
From U.S. Pat. No. 4,892,014, a method is known, according to which the parking lock of the transmission is automatically engaged by the electric motor if an ignition circuit of the motor vehicle is interrupted and at the same time the vehicle speed is lower than a defined low threshold value, but also if the driver door of the motor vehicle is open and at the same time no weight is applied to the driver's seat of the motor vehicle and the vehicle speed is below the small threshold value mentioned above. In both cases it is provided that during the automatic engagement of the parking lock, additionally a parking brake of the motor vehicle is automatically actuated. U.S. Pat. No. 4,892,014 also proposes to have the transmission automatically switched to the neutral position by the electric motor if the ignition circuit is closed without the driving motor of the motor vehicle running, without a drive request being necessary.
Finally, from EP 0 814 287 B1 a function for the automatic engagement of a parking lock of an automatic transmission is known, wherein the parking lock in the automatic transmission is automatically engaged by the transmission control logic if the driving speed of the motor vehicle is zero and simultaneously an ignition circuit was interrupted, and as an additional condition, either a predetermined time period after the interruption of the ignition circuit has passed, or a vehicle door is opened, but no later than when—this then being the only condition—the ignition key is removed from the ignition lock. In order to achieve better vehicle availability, in all three cases according to a special characteristic the engagement of the parking lock is prevented if the driver selected the neutral position using the selector lever directly before shutting off the engine or within a predetermined time period after shutting off the engine.
It is the object of the present invention to create a method for automatically selecting a neutral position in an automatic or automated transmission of a motor vehicle and for automatically selecting a parking device of the motor vehicle intended for immobilizing the motor vehicle, the method being an alternative to the state of the art, having sufficient safeguarding of the motor vehicle against any start-up or movement that is not intended by the driver, and also having the least possible impairment of the drivability or maneuverability of the vehicle, while avoiding changes in the operating state of the transmission and/or the vehicle which come as a surprise to the driver.